The disclosure was greeted with relief on Wall Street, where investors bid up Allstate shares 40 cents, or 0.85 percent, in late-morning trading on a day when the indexes were broadly down. Shares fell in the afternoon to close at $25.10, down 1.10 percent; the Dow slid more than 300 points.

For April and May combined, Allstate said catastrophe losses were an estimated $539 million combined on a pretax basis.

In the second quarter of 2012, Allstate reported $820 million in pretax catastrophe losses and $440 million for just June of that year.

In Oklahoma, Allstate's losses were likely minimized by its relatively low market share in that state. Allstate is the fourth-largest insurer of homes in the Sooner state, while it's the second-largest nationally.